The New Horizons Geometry Visualizer: Planning the Encounter with Pluto

Transcription

1 The New Horizons Geometry Visualizer: Planning the Encounter with Pluto IDL User Group October 16, 2008 LASP, Boulder, CO Dr. Henry Throop Sr. Research Scientist Southwest Research Institute Boulder, CO

2 NHGV: New Horizons Geometry Visualizer The New Horizons Mission to Pluto NHGV: Brief demo and overview Developing NHGV in IDL

3 New Horizons Spacecraft LORRI (Visible Imager) REX (Radio Experiment) ALICE (UV Spectrometer) PEPSSI Ralph (Visible/IR Imager/Spectrometer) SWAP (Solar Wind) Student Dust Counter $700M NASA-funded mission Lead institution: SwRI 2006 launch; 2015 Pluto

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6 New Horizons iphone Camera 1 MP 2 MP Storage 16 GB 16 GB Network Battery NASA Deep Space Network 88 years, Plutonium-238 3G 4 hour

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9 Pluto-Charon July 2015 Jupiter System March 2007 KBOs Launch January 2006

10 What does GV do? GV is a virtual planetarium of the Solar System, as seen from a moving spacecraft. Answers questions like: When can we fit Pluto and its satellites into a single frame? What stars are visible when the Sun passes behind Charon? What is the sub-solar longitude on Pluto at closest approach? On what day should we approach Pluto so as to see the whole planet? Designed as a sandbox for planning observations. Not used to program commands into spacecraft.

11 GV Design Goals Priority 1: Accuracy Priority 2: Features Ease of use Speed Ease of development Ease of distribution

12 Existing Programs STK JPL tools Proprietary; Expensive ($70K/seat); Overkill for most users Minimal support; Some Solaris only Not SPICE-based Other tools Not customizable

13 GV is Web-Based Works on all hardware platforms Works from anywhere in the world All users are guaranteed to be using up-to-date version. All support files (kernel files, documentation, etc) are kept in sync. There are hundreds of frequently updated kernel files, and user-maintained local repositories are prone to be out-of-sync!

14 Tour of GV

15 Realistic planet surface models

16 Star catalogs

17 Motion across the sky

18 Motion across the sky

19 Apertures of science instruments

20 Mosaics and uncertainty ellipses

21 Movies

22 Movies

23 Flowchart of GV System 2000 lines 100 lines 15,000 lines

24 Web Interface ION (IDL-on-Net) is a discontinued product, so we can t use it! Instead, we use regular IDL, on a Linux Apache server. PHP code draws web page, waits for user input. HTML, not widgets! IDL starts up, runs, creates output files, and exits. PHP reads these files and displays to screen. Requires starting up IDL at every web call, but more robust than other options.

25 PHP code generates HTML front end

26 PHP code generates HTML front end

27 PHP is interface between user and IDL

28 csh scripts: Invoke IDL and log output

29 Flowchart of GV System 2000 lines 100 lines 15,000 lines

30 SPICE * (*) SPacecraft, Instrument, Camera kernels SPICE is a spacecraft geometry toolset developed and maintained by NASA-JPL. Highly accurate astrometric / geometric computations. Hundreds of functions. Distributed for C, FORTRAN, IDL. SPICE is the standard for interplanetary spacecraft navigation. Kernel files define trajectories, ephemerides, FOVs, leap-seconds, planet masses, etc. Using SPICE assures that everyone gets the same results!

31 ICY is the name for the IDL version of SPICE library

32 A few sample SPICE routines...

33 GV Parameter file Values entered by user. File generated by PHP. Read and processed by IDL: Compiled on-the-fly and executed as IDL code.

34 Map Projections

35 Albedo maps

36 Composition maps

37 Longitude systems IAU vs IDL longitude systems Most go , not 180 W, 180 E Some have N pole in different directions Spherical bodies only

38 Cartesian Projection

39 Stereographic projection

40 Stereographic projection

41 Multiple stereographic projections

42 Things that Worked SPICE Robust and powerful; forms the basis of all of GV s computations. Calling IDL from Web, using PHP interface Unix shell utilities and external functions File management Star catalog searches Movie encoding IDL: Rapid development, etc.

43 Things that didn t work as easily... Direct Graphics: should use Object Graphics! Higher quality Much faster 3D rendering than direct graphics. More flexible text labels. Direct graphics has bugs, quirks. Polyfill works differently on Mac, Unix [1,1] pixel works differently on X, Zbuffer Clipping works differently on X, Zbuffer IDL s map routines support Earth s longitude system but not other planets IDLDE (Workbench) is nice but no easy integration with VIM editor

44 Onward...